With the development of technology, it has been booming up for research and development of a head-mounted display apparatus (Head Mount Display, HMD), which provides users full immersion of a virtual scenario without outside interference by enlarging an image from a display screen and presenting such an enlarged virtual image in front of human-eyes at a certain distance via a set of optical system. As an important component, the optical system is required to not only guarantee high resolution of image quality but also provide wider field-of-view due to characteristics such as a compact structure and lightweight, which make the head-mounted display apparatus to be portability.